THE LODE. 267 



but with a general strike of about north 15° east. At each extremity of 

 this main tissure the Lode ramifies into diverging branches, of which tliere 

 are two at the south end, and a greater number, probably more than are 

 shown, at the northern extremity. These branches dwindle as the distance 

 from the main body increases, and finally disappear, though it is not im- 

 possible that they might be traced somewhat farther than the map shows 

 them. The whole system produces upon the eye the impression of a crack 

 in slightly elastic material, due to a force acting near the middle and equal- 

 ized at the extremities by dissemination over a large area. This impression 

 is probably correct. The fissure has a comparatively counStant dip of from 

 33° to 45°, though there are local irregularities of a trifling character. 



Prismatic horse. — A vcry interesting and important feature of the Comstock, 

 observable in cross-section, is the forking of the vein at some distance be- 

 low the croppings. The foot wall continues in typical cases unbroken to 

 the surface, but a secondary fissure rises through the hanging wall in a 

 more or less nearly vertical direction, leaving the foot wall at a depth of 

 several hundred feet. A mass of country rock, which might be represented 

 diao-rammatically as a triangular prism, is thus included within the external 

 walls of the vein. It is needless to say that very considerable modifications 

 in the direction, position, and geometrical form of the secondary fissure are 

 observable in different portions of the Lodk. 



Vein below the horse. — Exccptlug iu the rcgiou abovc the junction of the 

 east and west fissures, the vein in dip is of very uniform thickness; and 

 does not show as often or as prominently as many lodes the tendency to 

 open into chambers and pinch out again, which commonly accompanies a 

 faulting of one wall relatively to the other. This fact is by no means due 

 to the absence of a fault, but to its especial character. There is an un- 

 mistakable similarity between the configuration of the west wall and that of 

 the eastern face of the range. 



The walls. — The hanging wall of the Comstock is diabase throughout the 

 entire 10,000 feet of the main Lode, for some distance on the southeast 

 branch, and along its northeast 1:)ranch, as far as the explorations have been 

 can-ied. The east wall is almost all in an extreme state of decomposition so 

 far as the bisilicates are concerned, and the feldspars also are frequently 



